Doors are used for partitioning spaces, such as inside and outside of buildings, rooms in a building, a control cabin and a passenger cabin in airplanes, and hotel rooms. Such doors are often provided with locks for the purpose of protection of privacy or security.
Some types of the doors with locks for protecting rooms are openable by simply rotating a handle or knob on the doors from inside the room, but requires releasing of the locks for opening from outside the rooms for security. Some types of the locks are released by using keys or magnetic cards, and some other types are released by pressing buttons or turning a dial in predetermined directions, in accordance with a predetermined secrete code, which the opener of the door must memorize. When the lock is released in such a way, the door is openable by rotating and pulling or pushing the handle or knob.
Recently, push button locks are often used, in particular for the door between the passenger cabin and the control cabin of jet airplanes for security. In some cases, the secrete code for releasing the lock is changed even for each flight for preventing unauthorized opening of the door. Such push button locks are disclosed, for example, in JP-58-80074 and JP-11-256896, the latter being an improvement of the former.
When the door is locked with such a lock, the door cannot be opened from the passenger cabin side without releasing the lock. For example, in case an intentional explosion occurs in the passenger cabin of a jet airplane and the air pressure in the passenger cabin is suddenly increased, if the door and the door frame partitioning the passenger and control cabins are firmer than the explosive power, the windows, doors, or even a part of the fuselage on the passenger cabin side may be destroyed. Then the air pressure in the passenger cabin is suddenly lowered due to exposure to the surrounding atmosphere, which endangers the passengers.
Further, in case the windows on the control cabin side are damaged, and the air pressure in the control cabin suddenly decreases, the door between the control and passenger cabins may be destroyed, and hit the instruments and gauges or the pilots, causing loss of flight controls.
When an explosion happens in an hermetically-sealed room, the door of the room may be destroyed, and not only the room itself but also the entire house or building may also be destroyed, resulting in serious human damage.